Conventionally, an image synthesizing system for synthesizing a pseudo three-dimensional (3-D) image through a computer graphic technique is known. Such an image synthesizing system is broadly used as in various video games, airplane and other vehicle maneuvering simulators.
FIG. 12 shows the principle of such an image synthesizing system. The image synthesizing system previously stores image information relating to a 3-D object 310 in a virtual 3-D space 300. The image information relating to the 3-D object 310 previously stored in a memory as a shape model comprises a plurality of polygons (1) to (6) (polygons (4) to (6) are not shown).
If the image synthesizing system is used in a driving game, the 3-D object 310 may be in the form of a racing car which moves in the virtual 3-D space 300 while competing with a player's car or in the form of a stationary matter such as a road, house or the like which is disposed in the virtual 3-D space.
When a steering wheel or the like in a control panel 314 is maneuvered by a player 312, the view point of a driver (player) which is set in the virtual 3-D space 300 corresponding to the player's car is varied in position and direction. 3-D objects representing the racing car competing with the player's car and the surrounding matters are perspectively projected on a perspective projection screen 316 of view-point coordinate system and displayed as a pseudo 3-D image 318. Thus, the 3-D objects including the racing car and other matters can be rotated and translated in real time by the player 312 to perform a simulation in the virtual 3-D space while viewing it from the driver (player).
There is also known an improved image synthesizing system using a so-called texture mapping technique. As shown in FIG. 3, such an image synthesizing system separates image information relating to a 3-D object 310 represented as a shape model which comprises in combination with a plurality of polygons and graphic information to be applied to the polygons forming the shape model (hereinafter called "texture information") and stores the shape model and the graphic information. When an image is output, texture data 340, 342 are applied to the respective polygons to synthesize the image.
According to such a texture mapping technique, the patterns and colors of a graphic can be processed intricately without increasing the number of polygons to be processed.
It is desirable that such a real-time display type image synthesizing system can synthesize a high-quality image while reducing the burden on the hardware.
However, the image synthesizing system of the prior art has the following problems.